1. Field of the Invention
The present invention relates to a semiconductor memory and in particular to a static random access memory (SRAM).
2. Description of the Related Art
As described in Japanese Patent Laid-Open Publication No. 2003-132684, the SRAM cell can be classified into two types. One is a single port SRAM cell including an input/output port for a single data transfer. Another is a multi port SRAM cell including a plurality of input/output ports for a plurality of data transfers. Further, the multi port SRAM cell can be classified into two types. One is a one read and one write SRAM cell including a single write port and a single read port. Another is a one read and two write SRAM cell including the two write ports and the single read port.
The typical semiconductor memory includes the plurality of SRAM cells arranged in an array. Therefore, when the start row address of sequential data to be written is even and the end row address of the sequential data is odd, the sequential data are written in the plurality of SRAM cells disposed over a plurality of rows. If the plurality of one read and one write SRAM cells are used for the semiconductor memory, the data associated with even row address are unintentionally written in the SRAM cell of which the row address is odd. Or, the data associated with odd row address are unintentionally written in the SRAM cell of which the row address is even. Accordingly, the semiconductor memory, such as the buffer memory, used for storing such sequential data has necessarily used the plurality of one read and two write SRAM cells or the plurality of two read and two write SRAM cells. However, the one read and two write SRAM cell and the two read and two write SRAM cell are more expensive than the one read and one write SRAM cell.